How many ports are on the CompTIA A+ exam?

The 220-1201 (Core 1) objectives list 14 protocols with their ports: FTP 20-21, SSH 22, Telnet 23, SMTP 25, DNS 53, DHCP 67/68, HTTP 80, POP3 110, NetBIOS 137-139, IMAP 143, LDAP 389, HTTPS 443, SMB 445 and RDP 3389. They also test whether each one uses TCP or UDP.

Both, on port 53. DNS uses UDP for ordinary lookups and TCP for zone transfers between DNS servers and for replies too large for UDP. For A+, remember UDP 53 as the default.

What port does RDP use?

TCP 3389. Newer Remote Desktop clients also use UDP 3389 alongside it for smoother video, but 3389 is the number to know.

What is the difference between port 139 and port 445?

Both carry Windows file and printer sharing (SMB). Port 139 runs SMB over NetBIOS, the older method; port 445 runs SMB directly over TCP, which is how modern Windows does it.

Do I need to know SNMP ports for A+?

It's lower priority. SNMP (UDP 161 and 162) is not on the 220-1201 (V15) port list, though many port charts still include it. CompTIA says its objective lists aren't exhaustive, and SNMP is worth knowing for IT support work anyway.

What's the easiest way to memorize A+ ports?

Group them by job (email, web, remote access, file transfer, Windows file sharing and network services), drill them with flashcards in both directions, and test yourself with a matching question until each number comes back instantly.

Common port numbers for CompTIA A+

Updated October 2026

CompTIA A+ Core 1 (220-1201) lists 14 protocols with their port numbers in objective 2.1, from FTP on 20-21 to RDP on 3389, and expects you to know whether each one runs over TCP or UDP. All 14 are in the first table below with what each one does, followed by ways to remember them and free practice.

Every port in the A+ 220-1201 objectives

CompTIA A+ 220-1201 ports and protocols (objective 2.1)

Port	Protocol	TCP/UDP	What it does
20-21	FTP	TCP	File Transfer Protocol: moves files between computers. Port 21 carries the commands, port 20 the data. Unencrypted.
22	SSH	TCP	Secure Shell: encrypted remote command-line access. SFTP file transfers run over it too.
23	Telnet	TCP	Unencrypted remote command-line access, replaced by SSH.
25	SMTP	TCP	Simple Mail Transfer Protocol: sends email from a client to a mail server and between mail servers.
53	DNS	UDP (TCP for zone transfers and large replies)	Domain Name System: turns names like www.example.com into IP addresses.
67/68	DHCP	UDP	Dynamic Host Configuration Protocol: gives clients an IP address, subnet mask, gateway and DNS server. Servers listen on 67, clients on 68.
80	HTTP	TCP	Hypertext Transfer Protocol: unencrypted web traffic.
110	POP3	TCP	Post Office Protocol 3: downloads email from the server to one device, usually deleting the server copy.
137-139	NetBIOS/NetBT	UDP 137-138, TCP 139	NetBIOS over TCP/IP: older Windows name lookup (137), datagrams (138) and file-sharing sessions (139).
143	IMAP	TCP	Internet Message Access Protocol: reads email that stays on the server, kept in sync across devices.
389	LDAP	TCP	Lightweight Directory Access Protocol: looks up and updates users, groups and computers in a directory such as Active Directory.
443	HTTPS	TCP	HTTP Secure: web traffic encrypted with TLS.
445	SMB/CIFS	TCP	Server Message Block (CIFS is an older dialect of it): Windows file and printer sharing, run directly over TCP.
3389	RDP	TCP (newer clients also use UDP)	Remote Desktop Protocol: a full graphical Windows desktop over the network.

SNMP is not on the list. Many A+ port charts still show SNMP (161/162), but SNMP is not on the 220-1201 (V15) port list. You'll find it in the other-ports table further down, with the ones you'll meet on the job.

TCP vs UDP

Objective 2.1 also tests the two transport protocols themselves. TCP (Transmission Control Protocol) is connection-oriented: it opens a session with a three-way handshake, numbers every segment and resends anything lost, so data arrives complete and in order. UDP (User Datagram Protocol) is connectionless: it sends each datagram with no handshake and no delivery check, which makes it faster and lighter but leaves lost data for the application to deal with.

TCP: FTP, SSH, Telnet, SMTP, HTTP, POP3, IMAP, LDAP, HTTPS, SMB and RDP. Anything that has to arrive complete, like a file, an email or a web page, uses TCP.
UDP: DHCP and DNS lookups. DHCP has to use UDP: a computer with no IP address yet can't open a TCP connection, so it broadcasts. A DNS lookup is one short question and answer, so a lost packet is simply asked again.
Both: DNS switches to TCP for zone transfers between servers and for replies too big for UDP. NetBIOS uses UDP 137 and 138 for names and datagrams and TCP 139 for sessions. Newer Remote Desktop clients add UDP 3389 alongside TCP for smoother video.

On the exam, a protocol that needs a reliable session (logins, files, mail, web pages, directory queries like LDAP) is TCP; DHCP's broadcasts and quick DNS lookups are UDP.

Secure and insecure pairs

Several protocols on the list send everything, passwords included, as plain text. Scenario questions often ask for the secure replacement:

Telnet (23) to SSH (22). Both give remote command-line access; SSH encrypts the session.
HTTP (80) to HTTPS (443). HTTPS is HTTP inside TLS encryption.
FTP (20-21) to SFTP (22). SFTP moves files over an SSH connection, so it uses SSH's port.
LDAP (389) to LDAPS (636). LDAPS wraps directory lookups in TLS.
POP3 (110) and IMAP (143) to POP3S (995) and IMAPS (993). The TLS versions of the two mail-reading protocols.
NetBIOS (137-139) to SMB on 445. Not an encryption swap: modern Windows runs SMB straight over TCP 445 without NetBIOS, so 137-139 mostly serve older systems.

SFTP shares SSH's port 22, which is on the list. LDAPS, POP3S and IMAPS aren't on the 220-1201 port list; their numbers are in the other-ports table below.

Group the ports to remember them

Holding 14 unrelated numbers in your head is hard. Grouped by job, they become six short lists:

Email: SMTP 25 sends mail. POP3 110 and IMAP 143 receive it: POP3 downloads it to one device, IMAP keeps it on the server and syncs every device.
Web: HTTP 80, and HTTPS 443 for encrypted pages.
Remote access: SSH 22 and Telnet 23 sit side by side (the secure one comes first), and RDP 3389 gives you a full Windows desktop.
File transfer: FTP 20-21. Port 21 carries the commands, port 20 the data.
Windows file sharing: NetBIOS 137-139 for older systems, SMB 445 for modern ones.
Network services: DNS 53 turns names into addresses, DHCP 67/68 hands addresses out, and LDAP 389 looks up users and computers in a directory.

Drill them in both directions, number to protocol and protocol to number, because the exam asks both ways.

Other ports you'll see (not on the A+ list)

These ports aren't on the 220-1201 port list, so learn them after the ones above. CompTIA says its objective lists aren't exhaustive, though, and you'll meet these on the job and on many port charts. NTP and Syslog do appear in the objectives as server roles, just without their ports. Port numbers are from IANA's official port registry.

Other common ports, not on the A+ 220-1201 list

Port	Protocol	TCP/UDP	What it does
69	TFTP	UDP	Trivial File Transfer Protocol: simple file transfer with no login, used for network boot and device configuration files.
123	NTP	UDP	Network Time Protocol: keeps computer and device clocks in sync.
161/162	SNMP	UDP	Simple Network Management Protocol: monitors and manages network devices. Alerts (traps) arrive on 162.
514	Syslog	UDP	Sends log messages from devices and servers to a central log server.
636	LDAPS	TCP	LDAP over TLS: encrypted directory lookups.
993	IMAPS	TCP	IMAP over TLS: encrypted email reading.
995	POP3S	TCP	POP3 over TLS: encrypted email download.

Practice the ports

Free port-matching PBQ: Match Ports to Protocols is a free performance-based question from Core 1. Match each protocol to its port; it's graded instantly and needs no account.
Free practice questions: the TCP, UDP, ports and protocols section of the free Core 1 practice test, each question with a full explanation.
Flashcards: ports are a textbook case for spaced repetition. The A+ flashcards guide covers what to card and a daily routine that sticks.
The rest of Core 1: ports are one objective in 2.0 Networking. The Core 1 study guide walks all five domains.
Everything else to memorize: the A+ cheat sheet puts these ports on one printable page with Wi-Fi standards, cables, RAID, commands and other key lists from both cores.